Freezing process and apparatus for eliminating frost on the window of a carton



1 INSULATION Jam. 12, 1965 s. A. LEVITZ 3,164,966

FREEZING PROCESS AND APPARATUS FOR ELIMINATING FROST ON THE WINDOW OF A CARTON Filed Sept. 17, 1962 HQ I FREEZING PLATE CONTROLLED,HEATED PLATE l FREEZING PLATE FIE. 7

lo i l INVENTOR.

SIDNEY A.LEVITZ FREEZING PLATE BY his ATTORNEYS United States Patent 3 164,966 FREEZING PROCESS AND APPARATUS FQR ELIM- INATING FROST UN THE WINDOW OF A CARTON Sidney A. Levitz, 1628 Robin Road, Lebanon, Pa. Filed Sept. 17, 1962, Ser. No. 223,934

15 Claims. (CI. 62-62) This invention relates to a process and apparatus for freezing a packaged product without forming frost on a transparent window of the package. It is a continuationin-part of the copending application of Sidney A. Levitz, Serial No. 140,723, filed September 26, 1961 (now abandoned).

Many frozen foods are sold in packages having a transparent film or window on one side of the package through which the contents of thepackage can be viewed. Unfortunately, the freezing process tends to form frost on the inside surface of this window, obscuring the view of the packaged product. The frost results from condensation of the relatively warm, humid air entrapped within the sealed carton. Since warm air is capable of holding more moisture than cool air, as the entrapped air adjacent the walls of the carton is cooled during the freezing process to a very low temperature below the dew point, snow or frost is deposited on the inner surfaces of the walls of the package, including the inner surface of the transparent window. This snow or frost is objectionable because it defeats the very purpose for which the transparent window is provided.

In the process and apparatus of the present invention, the heat is withdrawn from the region of the package remote from the transparent film or window while maintaining the temperature within the package adjacent the transparent film or window above the dew point. By maintaining this differential temperature within the package during the freezing operation, the frost condensate tends to form within the package on surfaces remote from the window, leaving the transparent film or window relatively free of frost.

In a preferred embodiment of the present invention, the carton or package having the contents to be frozen is interposed between heated and freezing elements, the Window of the carton being in proximity to the heated element, permitting heat to be withdrawn from the carton or package from the wall opposite the window while preventing frost from forming on the inside of the window.

In another embodiment of the present invention, the heat is withdrawn primarily from the bottom of the package while a water filled bag is placed on top of the package against the outer surface of the transparent film or Window. Because of its high latent heat, the temperature of the water will remain in the liquid state at 32 F. for

a relatively long interval during the freezing operation, preventing the temperature within the package adjacent the transparent film or window from falling below the dew point while the temperature at the bottom of the package drops below the dew point. By the time the freezing process has been completed and the water within the bag has given up its latent heat and becomes frozen,

substantially all of the moisture will have been condensed within the package on surfaces remote from the transparent film or window.

The process and apparatus of the present invention is particularly suited for freezing meat products because the surface of the meat exposed to view through the window of the carton tends to retain its natural color, whereas in conventional freezing processes the upper surface of the meat exposed to view through the window may become dark due to oxidation of the blood coming to the surface or may become white due to the removal of too much moisture. The retention of the natural color of the meat is an ancillary and completely unexpected result of the undirectional freezing process of the present invention.

For a more complete understanding of the present invention, reference can be made to the detailed description which follows, and to the accompanying drawings, in which: 7

FIGURE 1 is a plan view of a tray used in carrying out the process of the present invention;

FIGURE 2 is a view of a tray cover showing a plurality of liquid-filled compartments on the underside thereof;

FIGURE 3 is a cross-sectional View taken on the line 33 of FIGURE 1, looking in the direction of the arrows;

FIGURE 4 is a cross-sectional view taken on the line ,44 of FIGURE 2, looking in the direction of the arrows;

FIGURE 5 is a cross-sectional view of the tray shown in FIGURE 1 containing a plurality of cartons and showing the cover of FIGURE 2 in operative position on top of the cartons;

FIGURE 6 is a perspective View showing a typical frozen products carton of the window type; and

FIGURE 7 is a schematic elevational view illustrating another form of the present invention.

The process of the present invention can best be described in conjunction with the related apparatus shown in the drawings. It is understood, of course, that the process is not limited to the use of this particular apparatus.

As explained above, the present invention is applicable to a process for freezing the contents of a package 10 (see FIGURE 6) of the type having a transparent film or window 11 on one side thereof through which the frozen contents of the package can be viewed. One package of this type is sold under the trademark Polarpac. The process, however, is also applicable to other packages and cartons of the window type, including trays wrapped in transparent film. In the references hereinafter made to cartons of the window type, this term is intended to include all of the various cartons and packages to which the present process is applicable, and is not intended as a term of limitation.

The cartons of the window type containing the product to be frozen are conveniently handled in large groups in a tray, 12 of the type shown in FIGURES 1, 3 and 5 of the drawings. The tray 12 includes a metal bottom 13 containing perforations 14 through which heat can be readily transferred, three upstanding side walls 15, and a hinged front door 16. The cartons with the products sealed therein are placed in the tray with the transparent windows facing upwardly, and an insulated cover 17 having an array of liquid-filled compartments 18 on the un-. derside thereof is placed on top of the transparent Windows.

can be made individually or in the form of one large bag subdivided by heat seals into the desired number of compartments; they are shown in FIGURE 2 of the drawings \as eight separate bags each subdivided by heat seals into two separate compartments with tacks 19 or other suitable fastening devices holding the bags to the underside of the cover.

In carrying out the process of the present invention, the cartons are placed in the tray 12 with the windows facing upwardly, and the cover 17 is placed on top of the cartons with the water-filled compartments resting against the outer surfaces of the windows of the cantons. The tray is then placed in a freezing chamber for a period of time and at a temperature which will depend upon the product to be frozen. In freezing small packages of meat products, the tray will ordinarily be left in the freezing chamber at a temperature of approximately 20 F. for about 16 hours. During the freezing process, the heat will be removed primarily from the bottoms of the cartons through the perforated metal bottom 13 of the tray. The insulated walls 15 and the relatively tight fitting insulated cover 17 tend to prevent heat transfer from the upper regions of the cartons in the tray. Moreover, the high latent heat of the water in the compartments of the cover helps maintain the temperature in the upper regions of the cartons adjacent the inside surfaces of the windows at a temperature above the dew point. This, therefore, establishes a dilferential temperature within the cartons and tends to deposit frozen condensate on the surfaces of the carton remote from the windows.

In practicing the process of the present invention, it is preferred that the freezing or above freezing temperature be retained adjacent the outer surfaces of the windows of the cartons until the product and air within the package is reduced to a temperature of approximately zero degrees F. or below.

In freezing small packages or meat products, the high latent heat of about 1 oz. of water in each of the waterfilled compartments will cause the water to remain in the liquid state and continue to give off heat for more than eight hours of a sixteen-hour freezing process at F. During this initial eight-hour period, substantially all of the moisture will have been condensed within the carton on surfaces remote from the window. Obviously, depending on the product to be frozen, the liquid content of the bags can be increased or reduced.

In practicing the process of the present invention, the trays are stacked one on top of another in multi-shelf racks which are transported to and from the freezing chamber. When the trays are thus stacked, the hinged front doors 16 permit the frozen product cartons to be introduced and removed from the trays without removing the covers 17. For purposes of convenience, the rack can be equipped with means to raise and lower all of the tray covers within the multi-shelf rack simultaneously.

The water-filled compartments incidentally, serve as a good indicator that the freezing process has been completed. If, for example, after a predetermined period of time it is observed that the water within the compartments remains in the liquid state, although it should have been changed to the frozen state, the operator is forewarned that the freezing process is not progressing in routine fashion.

After the freezing operation, the rack of trays is removed from the freezing chamber and the cartons are removed from the trays and cased. The racks, however, must be stored for approximately eight hours at a temperature of about 55 F. or higher to melt the iced contents of the compartments 18 of the cover 17. The humidity of the room in which the water-filled bags of the cover are defrosted should be regulated to a relatively low value to prevent excessive sweating of the bags.

A modified form of the invention is schematically shown in FIGURE 7 of the drawings. In this embodiment of the invention, a plurality of cartons 10 on a tray 20 is placed on a freezing plate through which a coolant is circulated. A heated element, such as a plate heated by an electrically heated coil, is spaced above the freezing plate, and the freezing and heated plates are relatively movable so that during the freezing operation the heated plate is adjacent the outer surface of the window of the carton while the heat is removed from the carton through the freezing plate in contact with the side of the carton opposite the window. In FIGURE 7, the apparatus therein shown includes several tiers overlying a lowermost freezing plate, each overhead tier including a lower heating plate, an upper freezing plate and insulation therebetween. When the trays full of cartons are placed on top of each of the freezing plates, the upper tiers are moved downwardly, as indicated by the arrows, to bring the overhead heated plates in close proximity to the windows of the cartons or packages 10. In this way heat is removed from the bottoms of the cartons when frost is prevented from forming on the windows at the tops of the cantons. When the freezing operation has been completed, the upper tiers are raised to permit the trays to be readily withdrawn.

The invention has been shown in a single preferred form and by way of example, and obviously, many modifications and variations can be made therein without departing from the spirit of the invention. The invention, therefore, should not be limited to any specified form or embodiment unless such limitations are expressly set forth in the appended claims.

I claim:

1. A process for freezing the contents of a carton of the window type without forming frost on the window comprising the step of subjecting the exterior of the carton to a reduced temperature to freeze the contents of the carton while maintaining the temperature adjacent the outside surface of the window at a temperature higher than the freezing temperature of water until the moisture within the carton has condensed on surfaces remote from the window.

2. A process as set forth in claim 1 in which the window side of the carton is insulated while the heat is withdrawn from the carton remote from the window.

3. A process as set forth in claim 1 in which the heat is withdrawn from the side opposite the window by a cold element while the temperature adjacent the outside of the window is heated by a heating element.

4. A process as set forth in claim 1 including the step of placing a liquid-filled container against the window of the carton while reducing the temperature of the contents thereof.

5. A process as set forth in claim 1 including the step of storing and displaying the carton in freezing condition at the temperature below the freezing temperature of water.

6. A process for freezing the contents of a carton of the window type without forming frost on the window comprising the step of reducing the temperature within the carton while maintaining a liquid-filled container against the outside of the window, the latent heat of the liquid within the container maintaining the temperature of the region adjacent the inside of the window at a higher temperature than the regions within the container more remote from the window.

7. A process for freezing the contents of a carton of the window type without forming frost on the inside of the window comprising placing the carton in a tray having insulated side walls and a heat transfer bottom, placing a liquid-filled container against the outside of the window, and placing the tray in a freezing chamber to freeze the contents of the carton.

8. A process for freezing the contents of a plurality of sealed cartons of the window type without forming frost on the insides of the windows comprising placing a plurality of the cartons in a tray having insulated side walls and a perforated, heat-transfer bottom, placing an insulated cover having a plurality of liquid-filled compartments on the underside of the cover on the plurality of cartons, and placing the tray in a freezing chamber for an interval of time long enough to freeze the liquid within the liquid-filled compartments of the cover.

9. An apparatus for freezing the contents of a carton having a transparent window in one side thereof comprising spaced apart freezing and heated elements,-the carton being interposed therebetween with the heated element adjacent the window and the freezing element adjacent a side remote from the window.

10. An apparatus as set forth in claim 9 including means supporting at least one of said heated and freezing elements for movement relative to the other to permit them to be separated to facilitate the introduction of a carton therebetween and to be moved toward each other for the freezing operation.

11. An apparatus as setforth in claim 10 including an insulated support carrying the freezing element above the support and the heated element below the support.

12. An apparatus for freezing the contents of a plurality of cartons, each having a Window in one side thereof, comprising a freezing plate on which a carton can be placed with its window at the top and at least one overhead tier including a lower heated element, an upper freezing element and insulation therebetween, and means imparting relative movement between the tier and the freezing plate to facilitate the introduction and removal of a carton therebetween.

13. An apparatus for freezing the contents of a carton having a transparent window in one side thereof comprising a freezing chamber, support means within said freezing chamber on which the carton can be placedv and heating means adjacent the outer surface of the Window of the carton thus supported toprevent condensation from forming on the inside of the window during the freezing process.

14. A process for freezing a meat product within a carton of the window type without forming frost on the Window and without discoloration of the surface of the meat product visible through the window comprising the steps of subjecting the exterior of the carton to a reduced ten1- perature to freeze the contents of the carton, and maintaining the temperature adjacent the outside surface of the window at a level substantially higher than the freezing temperature until the meat is frozen, the heat being removed and moisture within the carton being condensed and frozen remote from the window and the visible sur' face of the meat.

15. -A process for freezing the contents of a closed carton of the window type without frosting the inside of,

References Cited in the file of this patent UNITED STATES PATENTS 1,775,549 Birdseye Sept. 9, 1930 1,894,205 Stollsteimer Jan. 10, 1933 1,998,431 Birdseye Apr. 23, 1935 Taylor Mar. 31, 1953 

1. A PROCESS FOR FREEZING THE CONTENTS OF A CARTON OF THE WINDOW TYPE WITHOUT FORMING FROST ON THE WINDOW COMPRISING THE STEP OF SUBJECTING THE EXTERIOR OF THE CARTON TO A REDUCED TEMPERATURE TO FREEZE THE CONTENTS OF THE CARTON WHILE MAINTAINING THE TEMPERATURE ADJACENT THE OUTSIDE SURFACE OF THE WINDOW AT A TEMPERATURE HIGHER THAN THE FREEZING TEMPERATURE OF WATER UNTIL THE MOISTURE WITHIN THE CARTON HAS CONDENSED ON SURFACES REMOTE FROM THE WINDOW. 